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ARX-01 and ARX-03 Clinical Results Presented at the 30th Annual Scientific Meeting of the American Pain Society

REDWOOD CITY, Calif., May 18, 2011 /PRNewswire via COMTEX/ -- AcelRx Pharmaceuticals, Inc. announced today that the results from its Phase 2 clinical studies related to two product candidates, ARX-01 Sufentanil NanoTab(R) PCA System, which is designed to solve the problems associated with post-operative intravenous patient-controlled analgesia and ARX-03 to provide mild sedation, anxiety reduction and pain relief for patients undergoing painful procedures in a physician's office, will be featured in poster presentations at the upcoming American Pain Society Annual Meeting to be held in Austin, TX, on May 18th-21st, 2011. Commenting on the poster presentations, Pamela Palmer, MD, PhD, AcelRx co-founder and Chief Medical Officer said, "We are delighted that these data are being presented at this prestigious meeting by investigators involved in the studies. In particular, the combined data from ARX-01 Phase 2 studies highlight advantages of our post-operative pain management approach over existing methods that we hope to confirm in our Phase 3 studies."

Lead investigator, Harold Minkowitz, MD of the Memorial Hermann Memorial City Medical Center in Houston, TX will present analyses of the combined results from two randomized, placebo-controlled Phase 2 studies and one Phase 2 open-label system functionality study evaluating the safety and efficacy of the ARX-01 sublingual Sufentanil NanoTab(R) PCA System. ARX-01 is a non-invasive, sublingual alternative to intravenous patient-controlled analgesia (IV PCA). The results from the 212 patients included in these three studies indicate that ARX-01 was effective in treating both major orthopedic and major abdominal post-operative pain with minimal adverse effects.

Also presented will be results from a randomized, placebo-controlled Phase 2 study to evaluate the safety and effectiveness of ARX-03, a novel sublingual combination of sufentanil and triazolam that offers mild sedation, anxiolysis and analgesia for patients undergoing painful office-based procedures. Neil Singla, MD of Lotus Clinical Research in Pasadena, CA will present data from 40 patients who underwent elective low-volume liposuction. Administration of ARX-03 produced mild sedation and anxiolysis with rapid onset of effect, high physician and patient evaluations of effectiveness and tolerability, and a low incidence of side effects. Copies of these abstracts are available from the AcelRx Pharmaceuticals web site at www.acelrx.com/technology/publications.

About AcelRx Pharmaceuticals, Inc.

Based in Redwood City, CA, AcelRx Pharmaceuticals, Inc. (Nasdaq: ACRX) is a specialty pharmaceutical company focused on the development and commercialization of innovative therapies for the treatment of acute and breakthrough pain. AcelRx's lead product candidate, the ARX-01 Sufentanil NanoTab(R) PCA System, which has completed Phase 2 clinical development, is designed to solve the problems associated with post-operative intravenous patient-controlled analgesia (IV PCA) which has been shown to cause harm to patients following surgery because of the side effects of morphine, the invasive IV route of delivery and the inherent potential for programming and delivery errors associated with the complexity of infusion pumps. AcelRx has two additional product candidates which have completed Phase 2 clinical development: ARX-02 for the treatment of cancer breakthrough pain, and ARX-03 for providing mild sedation, anxiety reduction and pain relief for patients undergoing painful procedures in a physician's office.

Forward Looking Statements

This press release contains forward-looking statements, including, but not limited to, statements related to AcelRx Pharmaceuticals' statements related to clinical trial updates, effectiveness and advantages of its post-operative pain management approach and product candidate development. These forward-looking statements are based on the company's current expectations and inherently involve significant risks and uncertainties. AcelRx Pharmaceuticals' actual results and the timing of events could differ materially from those anticipated in such forward looking statements as a result of these risks and uncertainties, which include, without limitation, risks related to: the success, cost and timing of AcelRx Pharmaceutical's product development activities and clinical trials; its ability to obtain and maintain regulatory approval of its product candidates; its ability to obtain funding for its operations; its plans to research, develop and commercialize its product candidates; its ability to attract collaborators with development, regulatory and commercialization expertise; the accuracy of AcelRx Pharmaceutical's estimates regarding expenses, capital requirements and needs for financing; and other risks detailed in the "Risk Factors" and elsewhere in AcelRx Pharmaceuticals' Securities and Exchange Commission filings and reports, including its Annual Report on Form 10-K for the year ended December 31, 2010 and its Quarterly Report on From 10-Q for the three months ended March 31, 2011. AcelRx Pharmaceuticals undertakes no duty or obligation to update any forward-looking statements contained in this release as a result of new information, future events or changes in its expectations.